1. Field of the Invention
This invention relates to filtration systems which use filter media to remove materials in solution, and which include backwash systems or launders. Specifically, this invention relates to baffle systems associated with a launder for producing quiescence in fluid flow and removal of air to enhance settling of filter media from solution to reduce loss of media during backwashing.
2. State of the Art
Filtration systems which use granular filter media, such as sand or gravel, to remove solids or particulates suspended in fluid are well-known in the art. Such systems are often used in wastewater, cleanwater and oil/water separation systems. Filter media filtration systems typically include a tank having drainage apparatus in the bottom of the tank for discharging filtered fluid therethrough and granular media layered on top of the drainage apparatus.
In conventional operation, fluid to be filtered is introduced into the tank, and downward movement of the fluid through the granular media causes solids and particulate matter to accumulate in the media. The filtered fluid drains to the bottom and exits the tank through the drainage apparatus. After hours of operation, the solids and particulates which have accumulated in the granular media reduce the efficacy of the filtration system and must be cleaned.
The drainage apparatus at the bottom of the tank is typically configured to provide backwashing or reverse filtration in which water and air are flushed back through the drainage apparatus and upwardly through the filter media to remove the accumulated solids and particulates. Launders, also referred to as troughs, are positioned in the upper portion of the tank, above the filter media. As water entering from the drainage apparatus fills the tank, the backwash spills over into the launders and is carried away from the tank.
It is known that forcing water and air through the filter media during backwashing is the most efficient means of removing accumulated solids and particulates. However, turbulence from the air causes lighter filtration media to be dislodged from the bed, and it is eventually discharged into the launder with the backwash. A considerable loss of filter media can result.
Others in the field have designed backwashing systems to reduce the amount of media lost during backwash. Examples of various systems are disclosed in U.S. Pat. No. 3,353,676 to Hirsch, issued Nov. 21, 1967; U.S. Pat. No. 4,076,625 to Scholten et al., issued Feb. 28, 1978; U.S. Pat. No. 4,132,652 to Anderson et al., issued Jan. 2, 1979; and, U.S. Pat. No. 4,746,431 to Gibaud et al., issued May 24, 1988.
Baffle systems have been developed which deflect and direct fluid flow in the area of the launder. U.S. Pat. No. 4,076,625 discloses a system in which curved baffles are positioned on either side of a launder to provide restricted channels on either side of the launder thereby directing the upward flow of fluid in a manner to allow media to fall back into the tank. By restricting flow around the launder, the flow velocity is reduced below the settling velocity of the media and media settles back into the tank.
Most launder and baffle systems address only reduction of flow velocity as a means of promoting settlement of the media, and do not address direction of flow or the disposition of air in suspension as a means of further reducing turbulence and thereby enhancing settling of the media. Therefore, it would be an advancement in the field to provide structure associated with a launder which reduces flow velocity, which directs flow away from the launder and which provides dissipation of air from the fluid to promote more efficient settling of filtration media therefrom.